During the last few years, the concept of All-Digital Transmitters (ADTs) have attracted considerable attention from both the research and the industry community, due to their capability to design integrated, reconfigurable, agile, multiband and multi-standard transmitters in a highly-efficient and flexible way.
Switch mode PA (SMPA) is normally used to efficiently amplify the incoming digital signal to certain amplitude for a reliable wireless communication. Up to the input of SMPA, both power encoding and digital modulation can be implemented in digital domain, with high flexibility. Generally, a band-pass filter is needed to reconstruct a switch mode power amplifier (SMPA) output signal from digital waveform into analog waveform to meet the out of band spectrum regulations before emitted via antenna. Nevertheless, the underlying quantization process of power encoding is highly non-linear, and thus, a considerable amount of in- and out of band distortion is generated and must be considered in the design of the whole transmitter front-end.
Accordingly, there is a need to provide an improved digital TX for reducing quantization noise.